First use rate coding and recruitment of small motor units, then of intermdiate sized motor units, and finally of large motor units

First use the mechanism of rate coding and when all motor units are activated, they then use the recruitment 

First recruit small motor units, then recruit intermdiate sized motor units, and finally use recruitment and rate coding of large motor units

First use the mechanism of recruitment and when all motor units are activated, they then use the rate coding mechanism

First use rate coding of small motor units, then rate coding of intermdiate sized motor units, and finally rate coding and recruitment of large motor units